For many years ball propelling machines have been used as a training aid in a variety of sports. There are a number of different types of ball propelling machine presently available. However, three forms of ball propelling machine dominate the market. One type uses a pair of counter-rotating wheels to propel the ball, another uses a mechanical arm to throw the ball, and a third uses expanding gas, such as compressed air, to propel the ball from the machine.
U.S. Pat. No. 6,202,636 is an example of the third type, and describes a pitching machine which relies on expanding gas to propel a ball down a barrel towards an intended target. Some variability in the amount of spin imparted to the ball can be achieved by means of an adjustable friction surface which forms a portion of the barrel. Seamed balls such as baseballs are usually pitched in either a two or four seam (stitching) position, yet this is not taken into account in this machine. Accordingly, there exists a need in the art for a ball propelling machine that offers advantages in terms of ease of use and/or flexibility in terms of imparting spin and/or velocity to a baseball or the like propelled therefrom.